High brightness light emitting diode (LED) light sources are in high demand for challenging applications to replace conventional light sources that suffer from short life, poor efficiency and often contain toxic elements or compounds. We define an LED light engine as the combination of an LED board with LED die attached and a primary collection optic to, efficiently collect the light and substantially preserve the Etendue (solid angle, area, index squared product) and may include auxiliary electronics including temperature monitoring devices such as thermistors or thermocouples, photosenors for light monitoring, and drive electronics to control the LED drive current and voltage and an electrical connector. Prior art typically utilize tungsten or tungsten halogen, metal halide, and xenon arc lamps for related illumination applications.
Recently, LED based illumination systems have begun to appear in the market, but typically are based on prepackaged LED devices and suffer from relatively poor performance compared to the present invention.
Accordingly, it is a principle object of the present invention to provide a high brightness illumination source utilizing LEDs in combination with non-imaging collection optics.
It is yet another object of the present invention to provide an LED based system in which light is sampled from the output aperture of a collection optic and directed back to an on-board photosensor to allow for continuous monitoring or optical feedback control for applications that need to maintain constant light output or need to know how the light output changes with time and temperature.
Other objects of the invention will in part be obvious and will in part appear hereinafter when the following specification is read in connection with the appended drawings.